Welcome to the Forum, Karsan:
Check with the local law officials first, to see what is legal.
Some folks list their homes themselves and welcome Realtor interest at their own rate. Some make a deal with the Realtor in the begining for a lower rate of pay. If the house is priced right and there is a lot of interest, the Realtor knows he can turn a quick buck and may be glad to get 1-1/2% on the sale.
If they have to advertise the home, conduct open house, and have to show it more than 3 times they want the full rate; in some cases, up to 10% of the sale price. The key to a real estate sale is, if your home sells, it creates at least 4 more sales so, they don't have to make all their commission off you.